(a) Field of the Invention
This invention relates to a new or improved suction accumulator for use in air-conditioning systems including refrigeration systems and heating systems that include a heat pump.
(b) Description of the Prior Art
Closed-loop refrigeration systems conventionally employ a compressor that draws in gaseous refrigerant at relatively low pressure and discharges hot refrigerant at relatively high pressure. The hot refrigerant condenses into liquid as it is cooled in a condenser. A small orifice or valve divides the system into high-pressure and low-pressure sides. The liquid on the high-pressure side passes through the orifice or valve and turns into a gas in the evaporator as it picks up heat. At low heat loads it is not desirable or possible to evaporate all the liquid. However, liquid refrigerant entering the compressor (known as xe2x80x9csluggingxe2x80x9d or xe2x80x9ccarryoverxe2x80x9d) causes system efficiency loss and can cause damage to the compressor. Hence it is standard practice to include an accumulator between the evaporator and the compressor to separate and store the excess liquid.
An accumulator is typically a metal can, welded together, and often has fittings attached for a switch and/or charge port. One or more inlet tubes and an outlet tube pierce the top, sides, or occasionally the bottom, or attach to fittings provided for that purpose. The refrigerant flowing into a typical accumulator will impinge upon a deflector or baffle intended to reduce the likelihood of liquid flowing out the exit. There are many kinds of baffles and deflectors in the prior art, all designed to reduce liquid carryover (see for instance U.S. Pat. Nos. 5,78,7729, 5,471,854, 5,201,792, 5,184,479, 5,021,792, 4,768,355, 4,651,540, 4,270,934, and 4,229,949), and the prior art includes designs that claim not to need deflectors (U.S. Pat. Nos. 5,179,844, 5,471,854). However in current standard use most accumulators use a variation of the dome (U.S. Pat. No. 4474035) or xe2x80x9cDixie cupxe2x80x9d (U.S. Pat. No. 4,111,005) deflectorxe2x80x94usually because they are simple and cost-effective. The above mentioned patents are incorporated herein by reference, in their entirety. There remains a need for a deflector design that directs the flow of refrigerant in the best possible manner to separate the gas from the liquid and minimize liquid carryover.
The invention provides an accumulator providing a reservoir for liquid-phase of a heat transfer medium that circulates in a closed-loop air conditioning system, said accumulator comprising: a hollow container defined by a peripheral wall and closed upper and lower ends; a supply pipe for delivering the medium from an evaporator in mixed liquid/gaseous phase into an upper region of said container; a delivery pipe in said container for passing medium predominantly in gaseous phase, from said container to a compressor in said system, said delivery pipe having an open inlet area located in said upper region of said container; and a deflector positioned in said upper region, said deflector being configured to prevent liquid phase medium from said supply pipe from entering the inlet area of the delivery pipe; said deflector having a recessed underside defined by a depending peripheral skirt having an outline that is closely spaced with respect to said peripheral wall to define therewith an annular gap; said deflector skirt adjoining the periphery of an upper wall of the deflector, said upper wall being positioned to be impinged by medium delivered from said supply pipe and being configured to distribute radially and impart rotation to said medium, thus enhancing the separation of the liquid phase along the accumulator peripheral wall especially as the liquid and gaseous phase pass through the annular gap, the open inlet area of the delivery pipe being shielded within the recessed underside of the deflector. The deflector of the accumulator disclosed herein provides for rapid separation of the liquid and gas phases of the stream of refrigerant entering the accumulator through the supply pipe. The deflector prevents liquid refrigerant from entering the delivery tube inlet. To this end, the deflector preferably has an upper surface that is formed with a series of grooves or channels extending in spiral fashion from a central part thereof towards the periphery. The liquid and gaseous refrigerant impinging upon this upper surface are largely deflected outwards to the peripheral wall of the accumulator. In the prior art, utilizing a smooth deflector surface, some portion of the liquid phase would collect upon the wall and flow downwards through the annular gap between the deflector and peripheral wall. However, much of the liquid would remain entrained in (or be returned to) the gaseous stream and be transported into the delivery pipe. In the present invention the spiral grooves or channels on the deflector surface impart a rotation to the refrigerant stream as it is deflected. The higher centrifugal action of the denser liquid phase preferentially forces it to the peripheral wall, and the swirling of the liquid tends to keep it forced against the wall as the liquid flows downward through the annular gap between the wall and the deflector. The multiple spiral grooves tend to distribute the liquid evenly and ensure that rotation and radial motion will be imparted to all refrigerant impinging upon the deflector. The gas will also swirl smoothly through the annular gap, and the grooves on the underside of the deflector will tend to maintain this swirling and aid in the re-direction of the gas into the delivery tube inlet. The deflector thus effects superior separation of liquid and gaseous refrigerant, reducing liquid carryover, and smooths the gas flow, reducing deleterious suction-line pressure drop. The result is superior refrigeration system performance.
The outlet delivery tube may be of a conventional U-or J-shaped configuration, with one limb extending in an axial direction through hermetically sealed joints in the top of the accumulator and in the deflector, the other limb of the tube opening in a sheltered position beneath the deflector and the two limbs being joined through a curved bight portion located at the lower end of the accumulator. The configuration of this tube will vary depending on whether the tube is desired to exit the accumulator through the top, bottom, or side wall. Liquid refrigerant passing over the deflector will move under gravity to the lower end of the accumulator which constitutes a reservoir for the liquid. Compressor oil is contained in the liquid refrigerant, and it must be returned to the compressor. It is gradually entrained in known manner through a small orifice into the gas refrigerant stream that passes out of the accumulator through the U-tube.
The deflector may be fabricated in any suitable material such as aluminum, rubber, plastic, or composite material. The deflector may comprise or include material which acts as a desiccating element. The annular gap between the peripheral skirt of the deflector and the accumulator wall is preferably maintained by projecting ribs on the skirt which engage the wall and support the deflector relative thereto in rattle-free condition. It is preferable that these ribs are shaped to aid the swirling motion of the refrigerant flowing through the gap.
The inlet to the J-shaped delivery tube is preferably located in guides provided on the underside of the deflector, to maintain the position of the inlet with respect to the deflector, especially the spacing between the underside of the deflector and the inlet of the tube.
The deflector disclosed herein can be modified to suit any style of accumulator, including the xe2x80x9ctop in/top outxe2x80x9d style as herein after illustrated and described, as well as other types of accumulator identified as top in/side out, top in/bottom out, side in/top out, side in/bottom out, or side in/side out. This can be effected by changing the delivery tube and the fit of the deflector with respect to the delivery tube to suit the particular application.